The invention concerns a method for incorporating and accessing semi-structured data within an LDAP environment.
With the release of the Lightweight Directory Access Protocol (LDAP) version 3 in 1997 [M. Wahl, T. Howes, and S. Kille. Lightweight directory access protocol (v3). RFC 2251, December 1997. ], the popularity of directories to store information about users, networks, etc. has been steadily increasing. Even companies like Netscape or Microsoft offer LDAP support in their browsers and operating systems, making directory services a viable alternative to more traditional database systems for the storage and efficient retrieval of information. At the same time, the Internet community has been moving away from static HTML to describe information on the web, towards more dynamic and easily configurable options that allow the decoupling of content, usually represented in form of XML data [Tim Bray, Jean Paoli, C. M. Sperberg-McQueen, and Eve Maler. Extensible markup language (XML) 1.0 (second edition). www.w3.org/TR/2000/REC-XML-20001006, October 2000.], and format, usually represented as CSS data [Hakon Wium Lie and Bert Bos. Cascading style sheets, level 1. www.w3.org/TR/REC-CSS1, January 1999.]. This transition has lead to an increase in the involvement of the database community in issues related to semi-structured databases [H. V. Jagadish, Laks V. S. Lakshmanan, Tova Milo, Divesh Srivastava, and Dimitra Vista. Querying network directories. In SIGMOD 1999, Proceedings ACM SIGMOD International Conference on Management of Data, Jun. 1-3, 1999, Philadephia, Pa., USA, pages 133-144. ACM Press, 1999], a reevaluation of semi-structured data models, and even to the creation of models and mechanisms to efficiently represent and process semi-structured data in relational database systems [Albrecht Schmidt, Martin L. Kersten, Menzo Windhouwer, and Florian Waas. Efficient relational storage and retrieval of XML documents. In Proceedings of the Third International Workshop on the Web and Databases, pages 47-52, Dallas. Tex., May 2000. Khaied Yagoub, Danlela Florescu, Valerie Issamy, and Patrick Valdurlez. Caching strategies for data-intensive web sites. In Proceedings of the 26th VLDB Conference, Cairo, Egypt, 2000]. These relational systems have, nevertheless, limitations due to differences in the representation and query model [Jayavel Shanmugasundaram, Kristin Tufte, Gang He, Chun Zhang, David DeWitt, and Jeffrey Naughton. Relational databases for querying XML documents: Limitations and opportunities. In Proceedings of the 25th VLDB Conference, Edinburgh, Scotland, 1999.] that support the need for XML processing systems closer to its semi-structured nature.
In view of this prior art, it is the underlying purpose of the present invention to present an architectural design, query model and experimental results for a hierarchical distributed caching system based on LDAP technology developed to:                Improve the performance of data retrieval of sites based on XML technology;        Improve the current state of caching technology on the Internet by providing a system that supports both older and newer technologies; and        Serve as an example of a real world application on top of Plexor, a generic middleware framework for distributed applications.        